class Solution {
public:

    bool IsPopOrder(vector<int>& pushV, vector<int>& popV) {
        int pushi = 0, popi = 0;
        stack<int> st;
        while (pushi < pushV.size()) {
            st.push(pushV[pushi++]);
            while (!st.empty() && st.top() == popV[popi]) {
                ++popi;
                st.pop();
            }
        }
        return st.empty();
    }
};